The present invention relates to an ethanol extract from the leaves of the South African plant Helichrysum odoratissimum. The extract of the invention has been shown to have in vitro cytotoxic activity against A431 (epidermoid carcinoma) cells, as well as antioxidant activity.
Cytotoxicity of the extract was determined using the XTT (Sodium 3′-[1-(phenyl amino-carbonyl)-3,4-tetrazolium]-bis-[4-methoxy-6-nitro] benzene sulfonic acid hydrate) colorimetric assay. The XTT cell proliferation kit measures the reduction in viable cells in the presence of the plant extract. The extract showed strong cytotoxic activity against the A431 cells with a 50% inhibitory concentration (IC50) of 15.5±0.15 μg/ml.
Antioxidant activity of the extract was determined using the DPPH (1,1-Diphenyl-2-picryl hydrazyl) assay. The extract exhibited a high radical scavenging activity with an IC50 value of 5.13±0.07 μg/ml, which was observed in a dose-dependent manner.
According to the World Health Organization (WHO) 65-80% of the world's population in developing countries depends solely on plants for their primary health care needs. This is mainly due to the inaccessibility of poor income countries to access modern western medicines (Tag et al., 2012). In South Africa traditional herbal medicine is the primary source of healthcare for rural areas. It is estimated that approximately 27 million South Africans still rely on traditional medicine (Street et al., 2008). Traditional medicine is most prevalent in areas where Western health care is inaccessible or comparability higher in cost to traditional medicines. However the main reason for the high usage of traditional medicine is as a result of cultural beliefs (McGaw et al., 2005). Due to South Africa's large plant diversity it has been estimated that approximately 3000 plant species are used for their medicinal purposes (Light et al., 2005).
Cancer is one of the leading causes of death worldwide. In economically developed countries cancer is the leading cause of death whereas in developing countries it is the second leading cause. The prevalence of cancer is increasing in developing countries due to an increase in population and aging of the general population as well as adopting unhealthy lifestyles such as smoking, physical inactivity and unhealthy diets. Statistics based on GLOBOCAN 2008 estimate that approximately 12.7 million cancer cases and 7.6 million cancer deaths occurred in 2008 worldwide, of these cancer cases approximately 56% of cases and 64% of deaths occurred in the economically developing world (Dermal et al., 2011).
According to the World Health Organisation skin cancers, including non-melanoma and melanoma type cancers have increased over the past ten years. Worldwide there has been an estimate of 2-3 million non-melanoma skin cancer and 132,000 melanoma cases diagnosed in this period. The World Health Organisation further estimates that one in every three cancers diagnosed is a type of skin cancer.
Helichrysum odoratissiumum (L.) Sweet is from the Asteraceae family. It is a herbaceous shrub which is commonly known as Imphepho. This shrub is branched, has a strong aroma and is perennial which can grow to heights of 50 cm. The plant has silvery coloured leaves which are covered in fine hairs and yellow flowers which group at the tips of branches. H. odoratissimum has a wide geographical distribution in South Africa. It is also distributed in several other African countries including, Lesotho, Malawi, Mozambique, Swaziland and Zimbabwe.
H. odoratissimum has several medicinal traditional usages. The leaves and stems are burnt and the smoke inhaled which acts as a sedative or is used to treat insomnia. The roots are used to treat coughs and colds and an extract of the roots may be orally administered as a colonic cleanser. The ash of leafy twigs may be ingested and used to relieve coughs. Further, the ash obtained from the leaves may also be ingested to relieve vomiting. A tea from leaves is used to treat colic and stitch. Extracts or sap from the leaves and twigs of the plant may be used as eye drops to treat conjunctivitis. A decoction of the plant material is used to treat abdominal pains, female sterility, menstrual pain and/or eczema. An extract from the aerial parts of the plant is used to treat symptoms of dehydration. An infusion of leaves can also be used to treat symptoms associated with fever. In some cultures the plant is boiled and the extract obtained in this manner is used as an ointment for the treatment of pimples (Laurens at al., 2008).